Abstract Body (Do not enter title and authors here): Background: Increased mitochondrial ROS is a known contributor to endothelial cell (EC) dysfunction, which plays a major role in the development and progression of pulmonary hypertension (PH). MnSOD deficiency has been linked to pathological pulmonary vascular remodeling in PH, which overloads the right ventricle (RV), causing RV hypertrophy.
Hypothesis: We hypothesize that overexpression of MnSOD in ECs is effective in attenuating the progression of pulmonary hypertension and right ventricular hypertrophy.
Methods/Approach: We studied transgenic mice with EC-specific MnSOD overexpression inducible by a Tet-OFF system. Mice of both sexes were divided into two groups (n=7/group): MnSODVE-NE (normal expression of MnSOD in EC) and MnSODVE-OE (overexpression of MnSOD in EC). Monocrotaline (60 mg/kg, s.c.) was injected once weekly for four weeks in mice. PH was induced in both groups by weekly subcutaneous injection of monocrotaline (60 mg/kg) for 4 weeks. At the end of this period, RV echocardiogram was assessed, and the heart and lungs were collected for morphometric, histological, and protein expression analyses.
Results/Data: MnSODVE-OE animals presenting increased MnSOD expression in EC showed decreased muscularization of pulmonary arterioles (by a 44% decrease in pulmonary vascular remodeling, (18.43±0.80 in MnSODVE-NE vs. 10.27±0.87 in MnSODVE-OE, p=0.0001), 11% decrease in RV hypertrophy (0.31±0.01 in MnSOD-NE vs. 0.27±0.006 in MnSODVE-OE, p=0.0164), and 44% decrease in pulmonary vascular remodeling (18.43±0.80 in MnSOD-NE vs. 10.27±0.87 in MnSOD-OE, p=0.0001). Echocardiographic assessment showed a 25% increase in PAT/PET ratio (0.24±0.01 in MnSODVE-NE vs. 0.30±0.02 in MnSODVE-OE, p=0.0276) and 49% increase in TAPSE (0.74±0.08 in MnSODVE-NE vs. 1.1±0.03 in MnSODVE-OE, p=0.0020), indicating that EC-specific MnSOD-OE was able to attenuate the development of RV hypertrophy in PH. In the RV, this was associated with 22% decreased expression of phospho-PLN (p-PLN^Ser16/Thr17) (0.621.8±0.057 in MnSODVE-NE vs. 1.014±0.102 in MnSODVE-OE, p=0.010506), 60% increase in calmodulin (1.0±0.22 in MnSODVE-NE vs. 1.6±0.05 in MnSODVE-OE, p=0.0270), and 50% increase in SERCA2 to PLN ratio (1.2±0.10 in MnSODVE-NE vs. 1.8±0.15 in MnSODVE-OE, p=0.0099).
Conclusion(s): EC-specific MnSOD-OE is effective in attenuating pulmonary vascular remodeling and RV hypertrophy by modulating expression of calcium handling proteins in PH.